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Journal of Geophysical Research Atmospheres
Article . 2003 . Peer-reviewed
License: Wiley Online Library User Agreement
Data sources: Crossref
MPG.PuRe
Article . 2003
Data sources: MPG.PuRe
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Interplanetary and solar surface properties of coronal holes observed during solar maximum

Authors: Zhang, J.; Woch, J.; Solanki, S.; von Steiger, R.; Forsyth, R.;

Interplanetary and solar surface properties of coronal holes observed during solar maximum

Abstract

Data from the Solar Wind Ion Composition Spectrometer (SWICS) on board the Ulysses spacecraft and synoptic maps from Kitt Peak are used to analyze the relatively short‐lived coronal holes which exist during the maximum phase of the solar activity cycle 23. They are compared with the persistent polar coronal holes which prevail around solar minimum. A solar wind velocity increase coinciding with a shift of the ionic charge composition toward lower charge states serves as a robust criterion for identifying solar wind streams emanating from solar maximum holes. This allows an unambiguous association of every stream identified in interplanetary space with a coronal hole on the solar surface with consistent magnetic polarity. Solar wind streams emanating from the solar maximum holes generally show lower velocities of 400 to 600 km/s compared to the polar hole stream velocities of 700 to 800 km/s. However, the SWICS O7+/O6+ charge‐state ratios, which are a proxy for coronal temperatures, do not reveal a consistent difference. Though a number of solar maximum holes have a significantly, up to three times, higher temperature compared to the polar coronal holes, the majority of the investigated holes and specifically those with new cycle polarity have a coronal temperature within the range of polar hole temperatures. Likewise, the magnetic flux density in the solar maximum holes and in the polar coronal holes, as derived from the synoptic maps, is not strikingly different. Therefore any intrinsic difference between solar maximum holes and polar coronal holes is small. The striking discrepancy in their kinetic properties, namely the slower velocity of the solar wind streams emanating from solar maximum holes, may partly be attributed to deceleration of the solar wind during propagation to the spacecraft. The discrepancy may also be influenced by active regions in close proximity to the coronal holes, which presumably is more likely for smaller holes. There may, however, be a tendency for the faster wind streams to emanate from cooler holes.

Related Organizations
Keywords

Sun and Heliosphere, ULYSSES: SWICS

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
23
Average
Top 10%
Top 10%
bronze